As mentioned in goodness knows how many other threads here and elsewhere, the problem isn’t the mere existence of “always evil” races, but rather, the existence of “always evil” races that are characterized in the same language and imagery as real-world bigoted stereotypes.  If you describe your always evil” races in words and images not linked to RW bigotry, then there’s no problem at all.
It really is that simple.
So the redcap isn’t an issue, not because it is Fey, but because it in no way is described as resembling a RW demographic.